A year after the disastrous Great East Japan Earthquake and tsunami devastated the northwest coast, wiping out villages, killing an estimated 20,000 people and precipitating multiple meltdowns at the Fukushima Daiichi nuclear plant, Tokyo’s 35 million residents are getting a severe case of earthquake jitters.

In part, of course, the nervousness may stem from memories of the March 11, 2011 shaking, reinforced by numerous one-year-on newspaper and television images of the still-stricken region, but it is also reinforced by new studies from respected institutions predicting that another “Big One” could strike the Tokyo area in four or five years.

These predictions from the University of Tokyo study have provided plenty of grist for doomsday newspaper stories, not to mention plenty of news-you-can use features about how to stock up on canned goods, flashlight batteries and other emergency supplies to tide one over in the event a massive quake hits the capital.

The advertising supplements of Japanese newspapers are full of ads for survival foods, flashlights, attachments to hook cabinets to walls to prevent their toppling over during a shaking. Many supermarkets have reserved whole aisles devoted to these products, some of which are fairly expensive.

Tokyo University based its analysis on the multitude of smaller earthquakes the region has experienced since Mar. 11. During the months of March-April, Tokyo experienced an average of one earthquake in the 4-5 magnitude every day, sometimes twice a day. They have tapered off considerably since then but a shaking is still felt every month or so.

Naoshi Hirata, one of the scientists, explained that the university’s prediction, though centered on Tokyo, the world’s biggest city, covered the entire Kanto Plain area, not just the downtown. It could strike as far as 100 km from the downtown or offshore, he maintained.

One might think that the Great East Japan Earthquake in the Tohoku region and resulting tsunami of which registered 9 on the Richter Scale was the Big One. After all, it was the biggest earthquake in Japan’s recorded history and one of the largest recorded anywhere at any time.

But it happened in the wrong place.

When Japanese refer to the Big One, they mean either a massive earthquake hitting Tokyo, as one did in on Sept. 1, 1923, or further south in Suruga Bay. The latter is a place where three giant tectonic plates rub together: The Eurasian plate, the Philippine Sea plate and the Pacific plate.

The last Big One occurred there in 1854, and Japanese records (which are pretty complete going back a thousand years), show that it recurs every 100-150 years. So it is due. Most of the country’s considerable investment in earthquake prediction is directed at predicting this anticipated cataclysm, also known as the Tokai Earthquake.

The most damaging earthquake in Japan’s history was the Great Kanto Earthquake in 1923. It measured 7.9 on the Richter Scale and devastated much of downtown Tokyo. More than 140,000 people died, most of them from fire, as the city was then made up much more wooden structure than now. Occurring exactly at noon, the shaking tipped over numerous hibachi, or charcoal fires preparing lunch.

A similar quake today would probably result in far fewer deaths, but would still cause enormous damage and disruption. Tokyoites got a taste of that a year ago, when the earthquake shut down Tokyo’s entire rail and subway system, leaving millions of the city’s residents to get home by other means, often by foot. More than a few spent seven, eight, nine hours walking home from work.

Japan has invested considerable effort in attempting to predict the net Big One. But most of the effort is focused first on the capital itself, and then on the area further south where the Philippine Plate pushes under the Eurasian Plate. This area also boasts another nuclear power plant complex, known as the Hamaoka site. Former Prime Minister Naoto Kan ordered the three plants closed in the weeks following the Fukushima crisis, fearing they would be exposed to another massive quake.

The Tohoku quake occurred in a different geologic neighborhood, where the Pacific Plate meets the Okhost Plate. Almost forgotten is that the mammoth March 11 quake was preceded by a shaking that registered 7.2 on the Richter Scale two days previously. It is almost unheard of for a quake of that magnitude to be followed by an even larger one, scientists say.

Meanwhile, new worries about another Tohoku earthquake arose when on Feb. 14 a team from the European Geosciences Union warned that the seismic risk to the Fukushima plants had increased because the underlying plates had readjusted to a more precarious position. The worry was that another 7+ quake might occur closer to the plant site.

These stricken nuclear power plants are now considered to be in a state “equivalent to a cold shutdown,” which means that the fuel is no longer overheating. But it is a fragile cold shutdown as the site manager Takeshi Takahashi has acknowledged. The cooling system was put together last summer in a hurry and is almost literally held together by duct tape and baling wire.

Additionally, the spent fuel pools of several containing radioactive fuel rods are located above ground and exposed to the elements. If the cooling system was interrupted by another power outage or the cooling displaced, a radiological fire could spew more radiation into the environment.

Tepco, the utility that owns the Fukushima plants, says it has prepared various contingency plans in the event that another quake hits the plant. “If the cooling system is knocked out, we’re prepared and will be able to handle it,” Takahashi said.